Studies on Pyrimidine Derivatives and Related Compounds. LXXV. Reactions of Thiazolium Salts with Diethyl Acylphosphonates and Hydroxylation of Some 3-Oxo-2, 3-dihydro-4H-1, 4-thiazine Derivatives

摘要: Reaction of simple benzothiazolium salts (V) with diethyl acylphosphonates (II) afforded ring-expanded products, 1, 4-benzothiazine derivatives (VII). In this reaction, it was found necessary to add II before triethylamine. VIIa-b were confirmed be identical authentic samples synthesized by the independent pathway shown in Chart 2. The reaction 4-methylthiazolium (XIII) 1 : adducts (XIV), which decomposed corresponding 4-thiazine (XV) alkaline treatment. Treatment 2-phenyl-3-oxo-4-benzyl-5-methyl-6-(2-acyloxy) ethyl-2, 3-dihydro-4H-1, (IV) hydrogen peroxide acetic acid gave 2-hydroxy-2-phenyl-3-oxo-4-benzyl-5-methyl-6-(2-acyloxy) (XIX).